Application of glass fiber and carbon fiber in wind turbine blades
Wind turbine blades are constructed from a variety of composite materials, primarily including reinforcing fibers, resins, core materials, and structural adhesives. The development of blade reinforcement materials has evolved from wood and metal to composite (fiber) materials. Studies have shown that under extreme wind speeds of 50 m/s, stress concentration and fatigue damage are common at the tip of megawatt-class blades in the spanwise 1/3 of the blade. Therefore, the selection of reinforcing fibers must simultaneously meet three requirements: withstand the extreme loads of 50-60 m/s gusts, guarantee a 25-year fatigue life, and achieve the stiffness control required for 100-meter blades (to reduce the risk of tower sweep). Currently, the main reinforcing fibers that meet these requirements in the wind turbine industry are glass fiber and carbon fiber.
Part 1 Glass Fiber
Glass fiber, due to its high strength, high modulus, and excellent resin impregnation, has become a core reinforcement material for wind turbine blades. According to statistics, my country's glass fiber market is expected to reach 120 billion yuan in 2023, with the wind power sector accounting for 30% (approximately 36 billion yuan). Continuous technological innovation by glass fiber manufacturers has resulted in significant improvements in material performance: the tensile strength of mainstream glass fiber models has increased by over 12% with each generation (Figure 1), contributing to blade lightweighting (e.g., a 15% weight reduction for 100-meter-class designs) and improving structural reliability. The tensile modulus has also increased by over 5% (Figure 2), enhancing deformation resistance (capable of instantly recovering from tensile forces of thousands of tons), supporting the large-scale and affordable development of offshore wind power.
Glass fiber has been used in the wind power sector for over 20 years. While technological advancements have driven industry development, the modulus of current ultra-high modulus products has reached 90% of the theoretical limit, making it difficult to meet the structural requirements of 100-meter and megawatt-class wind turbines. According to the Ministry of Industry and Information Technology's "New Materials Industry Development Guide" and data analysis from the International Composites Association, overcoming the performance bottlenecks of existing materials and developing new reinforcement materials have become key technological paths to promoting the large-scale development of wind power.
Part 2 Carbon Fiber
Carbon fiber composites offer significant advantages over glass fiber: tensile strength (3.5-7 GPa) and modulus (230-600 GPa) are increased by 2-3 times and 3-6 times, respectively, while density is reduced by over 30%. This helps lightweight wind turbine blades, extending the fatigue life of ultra-long blades (100-meter-long) by 40%, and improving overall turbine efficiency by 15-20%. The global carbon fiber industry is developing rapidly, with total production projected to reach 164,900 tons in 2025. Wind power demand will account for nearly 40,000 tons (24%), making it the largest application market (Figure 3). Its application in new energy equipment is expected to continue to expand.
Currently, technical barriers in the carbon fiber industry chain primarily focus on defect control of polyacrylonitrile (PAN)-based precursors and optimization of the carbonization process. These R&D cycles exceed 10 years, leading to market share concentration in leading companies. International leading companies include Toray and Mitsubishi of Japan, and Hexcel of the United States. Domestically, Jilin Chemical Fiber, Zhongfu Shenying, and Guangwei Composites are leading the industry, resulting in a highly concentrated landscape. Table 1 shows the main types and properties of carbon fibers used in wind turbine blades at home and abroad. As can be seen from Table 1, the tensile strength of carbon fibers used in wind turbine blades is generally between 4000 and 4500 MPa, and the tensile modulus is generally between 220 and 250 GPa. The overall performance is between Toray's T300 and T700 grades of carbon fibers.